RCU Review: FunKey Extra 300S


More On This Product

  • Show user ratings
  • Check for Retailers
  •  
     
    Contributed by: Greg Covey | Published: October 2003 | Views: 22427 | email icon Email this Article | PDFpdf icon

    Review by: Greg Covey

     



    Manufacturer: Fun-Key
    http://www.fun-key.com

    Distributed by:
    Yellow Aircraft International
    203 MASS Ave.
    Lexington, MA 02420
    http://www.yellowaircraft.com
    (781) 674-9898




    I first spotted the Extra 300S ARF in a magazine advertisement by Yellow Aircraft and I immediately noticed its classic sport plane looks. I then discovered that it was a 30-size scale ARF from Fun-Key Models and decided it would make a great conversion to electric power using an Astro Flight Cobalt motor. The attention to detail and degree of pre-fabricated work are impressive. All major components are pre-covered with Monokote. The fiberglass cowl is pre-cut, painted, and decaled. The plastic wheel pants are colored red to match the covering scheme. The undercarriage gear has been pre-painted and the control surfaces are all pre-slotted and hinged but not glued. The hardware set is complete with spinner, motor mount, fuel tank, wheels, and linkage parts.



    Kit Name: 30-size Extra 300S Aerobatic airplane
    Manufacturer: Fun-Key
    Price: $139 from Yellow Aircraft
    Wingspan: 1370 mm (53.9”)
    Wing Area: 31.7 dm2 (491 sq. in.)
    Length: 1100 mm (43.3”)
    RTF weight: 90 oz. (5.6 lbs.) on 18-cells
    Motor Used: Astro Flight 625G Cobalt motor
    (geared 1.68:1)
    Motor Controller: Jeti 450
    Batteries: 18-cells of CP1700SCR
    Prop Used: APC 13x6.5 e-prop

    When I first unpacked the plane, I measured the weight of some key components. They appeared to be both strong and relatively light for a glow-powered sport model.

    The manual looked very nice. It was a complete re-write from Yellow Aircraft about 20 pages long with 40-50 diagrams that showed key photos of the assembly process.

    The kit also includes a strip of matching red and blue shrink film covering for repairs. A roll of fiberglass mesh is included to reinforce the bottom wing joint after gluing the halves together.
    The finished wing is very solid yet reasonably light. The wing fits into plywood slots and is anchored at the trailing edge by two nylon bolts. The horizontal and vertical stabilizers are glued into place. The resulting assembly is very solid.

    I replaced the stock 2" wheels with 2-7/8" LYT73 wheels from Hobby Lobby for better grass takeoffs. This forced me to eliminate the pre-cut pants.

    The bottom view shows the nylon bolts and my Hitec HS-81MG (metal gear) servos. The rudder and elevator will get stronger HS-85MG (metal gear) servos. The HS-85MG servos would also work well for aileron controls.


    My AF625G Cobalt motor will fit nicely onto the firewall. The cowl is pre-cut, trimmed, and pre-painted. It is the best I've seen yet!
    • Fuselage = 11.0oz
    • Painted/decaled
      Fiberglass cowl = 2.0oz
    • Painted canopy = 1.3oz
    • Stabilizers, rudder,
      elevator total = 2.6oz
    • Alum landing gear = 2.7oz
    • Each wing half = 6.7oz

    I replaced the stock 2" wheels with
    3" LYT wheels for better grass takeoffs.
    This forced me to eliminate the pre-cut pants.


    The bottom view shows the nylon bolts and my HS-81MG (metal gear) servos.
    The rudder and elevator will get HS-85MG servos.
    By inspecting the inside of the fuselage, it was obvious that the construction quality was excellent. The turtle decks have balsa-wrapped covering over the struts and are then covered with 3 colors of shrink film. A very nice touch! The pre-painted landing gear is mounted to the fuselage with 4 bolts and captive nuts through light plywood blocks inside. It is very solid.

    The finished plane weighs 60oz with everything but battery cells. My 18 cells of CP1700 weigh 30oz and the all up weight is 90oz (or 5.6lbs).

    The Extra 300S has a 54" wingspan with a thin airfoil for low drag and high performance aerobatics.

    Mounting the Motor:

    MotoCalc Static Analysis

    The Astro Flight (AF) 625G Cobalt motor fit perfectly using the Sonic-Tronic #160 motor mount. This motor mount is both light and strong. In previous applications, I have used only tywraps to secure the AF625G motor to the Sonic Tronic mount. After a good hard run, the Cobalt motor becomes sufficiently hot to soften the tywraps and allow the motor thrust angle to change. To prevent this from happening, I used a stainless steel hose clamp (range 3/4" - 1 3/4") to secure the motor. I also added a balsa block between each brush holder and the firewall. This helps add motor support in the up and down directions. I was curioius to see what kind of power the motor was putting out, so I wipped out my Tac and measured 7600 RPMs at 31amps using 18-cells and an APC 12x8 e-prop.

    The additional .5oz in weight will be worth the security of keeping the motor in place. I also added two tywraps on either side of the hose clamp. The tywraps fit into the motor mount grooves per the original design and will keep the hose clamp from possibly sliding. The result is a very confident mount.

    Left:
    The stock tailwheel is both steerable and solid.

    Right:
    The split elevator has a "Y" linkage for independent adjustment of each half.

    Battery Removal Design:

    I split my 18 cells into 2 packs; one 10-cell and one 8-cell. The bottom 10-cell pack rests on the sturdy wing top. The 8-cell pack is then placed on top of the 10-cell pack. I attached a thin rubber pad to the wing top using servo tape. This helps to absorb any shock produced by the battery pack movement during flight. Both packs are then secured by foam blocks.

    To eliminate the receiver battery pack, I used the Ultimate BEC from Kool Flight Systems. The Ultimate BEC (UBEC) eliminates the need for a separate 4-cell Rx. battery pack by powering my receiver and servos right from the main flight packs. Both 35v and 45v versions are available for systems up to 37 cells. You no longer need to charge receiver packs and the UBEC is several ounces lighter than a 4-cell receiver pack. I held my UBEC to the top turtle deck struts using servo tape.

    I moved the rudder and elevator servos about 2" aft from the stock position to facilitate the battery placement. This made the linkage wires very short but they appeared to work just fine.

    Overall, it is a simple 1-2-3 insertion of pack1, pack 2, and foam block. The batteries can be swapped easily by removing only the canopy. There is no need to remove the wing except for traveling or storing the plane. My remaining task is to find a good way to replace the 4 canopy screws that currently hold it in place.

    Left:
    Placement of the servos and battery pack.

    Right:
    The white foam block is from a GWS R4-P recever case.

    This second picture shows the canopy cutout. The white foam block is from a GWS R4-P recever case. This foam is the lightest and firmest foam that I have seen. It is great for many R/C applications. I stuff the foam block inside last to hold the top battery pack.

    Overall, it is a simple 1-2-3 insertion of pack1, pack 2, and foam block. My remaining task is to find a good way to replace the 4 canopy bubble screws that currently hold it on place.

    Canopy Removal Design:

    My solution to easy canopy removal on the Extra 300S incorporated a combination of wooden dowels and rare earth magnets. I wanted a secure yet easy to remove solution for swapping battery packs without removing the wing. I used 6 sets of tiny rare earth magnets from Radio Shack.
    The tiny rare earth magnets are recessed into the fuselage and a matching set is epoxied onto the inside of the canopy. I drilled a hole through the canopy plastic to help the epoxy hold and then painted over it.

    To help secure the canopy from lifting due to wind forces during flight, I added a double wooden dowel prong to the front that slides into matching holes on the fuselage dashboard. I used 3 sets of magnets on each side. The combined 6 sets of magnets and wooden prong hold the canopy secure during rolls, snaps, and high speed runs.

    The canopy easily removes by pulling out the sides and sliding it back until the dowel rod has cleared the holes in the dashboard.


    My new Extra 300S was flown for the first time at a local meet on Memorial Day, 2002.

    We flew it 5 times and it was very stabile in flight! I wasn't expecting it to perform quite that well myself. The combination of a light and low drag airframe has made it a perfect housing for my AF 625G Cobalt motor.

    For the maiden voyage, I had my friend Lynn Bowerman fly the Extra. Lynn has many years of experience in flying high performance glow-powered sport models. Additionally, I wanted to see what the other guys at the field thought when the plane was given a real workout. After a short 25' takeoff, the plane went straight up into the air like a bullet! Everyone stopped what they were doing and came over to watch. I'll bet you can guess what the first question was..."That's electric?"

    I don't have power for unlimited vertical flight but the plane goes high enough for a proper stall turn in the sky where you start to loose perspective because it is so small.

    All the flights were with 18 cells of CP1700SCR and I was also surprised that the duration was longer than I had expected. Since the power level is so high, you can use good throttle management during the flight to prolong duration.


     

     

    My 30-size Extra 300S was a great fit with the Astro Flight 625G Cobalt motor. The 5.6lb sport plane is highly aerobatic and has reasonable flight duration with proper throttle management.

    The quality of the ARF kit was superb and Yellow Aircraft offers replacement plastics and fiberglass cowls separately. All the parts are pre-painted and covered. The Ultimate BEC eliminated the need for a receiver battery and reduced weight. Battery packs can be easily swapped by removing the canopy without having to remove the wing.

    This is a true scale design of the championship aerobatic full size model. R/C pilots that have high performance sport plane experience all know that nothing flies like an Extra!


    Manufacturer: Fun-Key
    http://www.fun-key.com

    Yellow Aircraft International
    203 MASS Ave.
    Lexington, MA 02420
    (781) 674-9898

    www.yellowaircraft.com

    Koolflight Systems

    355 Sunderland Circle
    Fayetteville, GA 30215
    (770) 486-1663
    www.koolflightsystems.com/ultimatebec.htm
    email: jsmeyers@earthlink.net

    Astro Flight
    13311 Beach Ave.
    Marina Del Rey, CA 90292
    (310) 821-6242
    www.astroflight.com
    email: info@astroflight.com

     


     

    Comments on RCU Review: FunKey Extra 300S

    There are no comments

    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

    EMAIL THIS ARTICLE OR CHECK OUT THESE OTHER GREAT REVIEWS!
     
    PhotoManufacturerProductSummaryReviewed
    Tower HobbiesJ-3 CubWith its distinctive looks, it is probably safe to say that the J-3 Cub is one of the most recognized and known airplanes in ...11/23/2015
    RCGF21cc Twin Cylinder Gasoline EngineRCGF, a Chinese manufacturer of gasoline engines, designs and manufactures engines specifically for 'the RC aircraft market. ...11/23/2015
    RCGF120cc Twin Cylinder Gasoline EngineRCGF, a Chinese manufacturer of gasoline engines, designs and manufactures engines specifically for the RC aircraft market. T...11/23/2015
    Seagull ModelsMaule Super Rocket 10-15cc ARFWhen Seagull Models announced that they were going to produce not just a model, but an ARF of the Super Rocket, I just had to...11/22/2015
    FliteworkEdge 540The Flitework Edge 540 is an electric only ARF airframe with a generous wing span of 66.9" and also beautifully dressed up in...11/21/2015
    Seagull ModelsSteen Super Skybolt 15cc ARFSeagull Models introduced this biplane early on in 2015, and SIG mfg. had a pre-production sample at the Toledo Expo. That pr...11/20/2015
    ST ModelSaltoST model brings us a fun aerobatic glider with the H101 Salto. The self-launch electric glider has no bad tendency and will b...11/19/2015
    RCGF10cc Gasoline EngineRCGF, a Chinese manufacturer of gasoline engines, designs and manufactures engines specifically for 'the RC aircraft market. ...11/17/2015
    Seagull ModelsFunky Cub 10-15cc ARFThe new Funky Cub has some really cool attributes, borrowed from scale aircraft, that should add up to make it a great flying...11/16/2015
    RCGF20cc Gasoline EngineRCGF, a Chinese manufacturer of gasoline engines, designs and manufactures engines specifically for 'the RC aircraft market. ...11/15/2015
    ST ModelASW28ST Model chose to reproduce the Schleicher ASW28, a single seater standard class glider capable of glide ratio up to 45. The ...11/10/2015
    The World Models30% PT-17 Stearman ARF (U.S. ARMY) Some may call me lucky. I would agree! One of the reasons that the PT-17 is so close to my heart is that I have a personal co...10/03/2015
    Bomberfield USA 201527th Annual B-17 GatheringEvery year, the end of the summer brings the big birds back to Monaville, TX, for a festive fly-in weekend at the local RC si...10/03/2015
    Seagull ModelsT-34 Mentor Seagull Models, distributed by SIG manufacturing in the US, has recently introduced their own version of this prop-driven mil...09/20/2015
    Seagull ModelsRadial Rocket ARFThis is the first in a series of Seagull aircraft that I will be reviewing for RCUniverse. Like the rest of the models that w...09/13/2015
     

      Return to Magazine Homepage






     
    RCUniverse is a service of Internet Brands, Inc. Copyright © 2001-2017.  Privacy Policy
     
    GET FREE RC CONTENT FOR YOUR WEBSITE

    Search | Marketplace | Event Central | Local Clubs | Magazine | Product Ratings | New Products | Discussion Forums

    Photo Gallery | Instructor Search | Field|Track|Marina Search | RCU Youtube Channel | | RCU Twitter!

    Member Locator | Advertisers | Hobby Vendor Resources | Rate Manufacturers | Sign In/Sign Up

    Products Videos WattFlyer.com RC Classifieds

    RCU4 | 54.205.65.73 | 0 | 1 | 09:09:11 AM EST | NC